1. Field of the Invention
The present invention relates to a method for connecting a lead wire and a lamp base of a lamp.
2. Description of the Prior Art
Conventionally, an incandescent lamp, a reflex lamp, a high-pressure discharge lamp, and a bulb-shaped fluorescent lamp are known as bulb-shaped lamps provided with a screw base or a bulb-shaped lamp base. For example, in a bulb-shaped fluorescent lamp, a lead wire for connecting a ballast circuit and a base is connected to an eyelet provided at the end of the base on the side of the base by soldering.
However, the connection with solder has a disadvantage in that a flux (resin) used for soldering may be formed into a film on a surface of the base end after the connection with solder and may cause corrosion or connection failure.
In recent years, as a connection method that avoids the use of lead for the environment protection purposes, a method using plasma arc welding to connect the base end and the lead wire has been under examination, and a technique for connecting the lead wire and the base with a plasma arc also is known (JP 62-73552A).
Generally, in the vicinity of the hole of the base through which the lead wire is drawn out, the end of the eyelet in the base is folded inwardly by drawing so as to prevent the lead wire from falling out of the base. For this reason, the top of the eyelet is substantially flat.
Then, a conductive shield plate having a hole is provided on the eyelet while the lead wire is latched on the folded portion at the hole of the eyelet. Then, the eyelet and the shield plate are electrically connected so that discharge is caused from a plasma nozzle onto the eyelet in the hole of the shield plate so as to generate a plasma arc. Thus, the lead wire and the eyelet of the base are fused by plasma arc welding.
However, the plasma arc can be generated in any position in the eyelet (which becomes conductive through the shield plate) or the shield plate itself. Therefore, it has been difficult to cause discharge stably in a position where the lead wire and the eyelet can be fused.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a method for producing a lamp that allows the lead wire to be fused with the base stably and satisfactorily by plasma arc welding.
A first method for producing a lamp of the present invention includes forming a tubular portion that is protruded in an eyelet of a base of a lamp; drawing a lead wire out of the tubular portion; and fusing the lead wire and the tubular portion with the eyelet by plasma arc welding. The protrusion of the eyelet in a tubular shape ensures that plasma arc is discharged to the protruded tubular portion. Further, the heat thereof melts the tubular portion and the lead wire so that the lead wire can be fused with the eyelet of the base satisfactorily and stably.
A second method for producing a lamp of the present invention includes mounting a sleeve onto a lead wire drawn out of an eyelet of a base of a lamp; and fusing the lead wire and the sleeve with the eyelet by plasma arc welding. This embodiment allows the use of a base having a conventional eyelet shape and ensures the plasma arc is discharged to the sleeve. Further, the discharge generates plasma, and the heat thereof melts the sleeve and the lead wire so that the lead wire can be fused with the eyelet of the base satisfactorily and stably.
It is preferable that the first and second methods for producing a lamp include placing a shield plate on the eyelet, the shield plate having a hole and provided with an insulator having an opening in the hole, in such a manner that the tubular portion or the sleeve is inserted into the opening of the insulator, before the process of fusing the lead wire and the tubular portion or the sleeve with the eyelet by plasma arc welding. This embodiment allows plasma arc to be discharged to the tubular portion or the sleeve stably, so that welding quality can be improved.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.